I have varying length, depending on the occasion. You can come to me or in me but you cannot touch me. I am three things yet only one at the same time. The end of me is in a cyclone yet not in a hurricane.

Michael Phelps, the famous swimmer can swim downstream in a lake in exactly 40 minutes (with the lake current helping his time). He can swim upstream in the lake in exactly 60 minutes (against the lake current). The length of the lake is two miles.